Question

If xy =c², then minimum value of ax + by is –

• A. c$\sqrt{ab}$
• B. 2c$\sqrt{ab}$
• C. – c$\sqrt{ab}$
• D. – 2c$\sqrt{ab}$

Answer 1

Answer: (B)

2c$\sqrt{ab}$

Answer 2

Q A.M. ³ G.M.

̃ $\frac{ax + by}{2}$ ³ $\sqrt{(ax)(by)}$

̃ ax + by ³ 2$\sqrt{ab}$c (\ xy = c²)

min value = 2$\sqrt{ab}$c